In general, in this kind of electric type automatic canceling devices for a winker, a winker operation lever pivoted by the operation knob is mounted pivotably on a case. A driving bar is held slidably by this lever through a compression spring so that this driving bar is thrusted with pressure on a cam, which is opposite thereto. As indicated in FIGS. 5A and 5B, this cam is composed of a fixed cam portion 23 and a movable cam portion 25 disposed in a slit 24 formed at the central portion of this fixed cam portion 23 so as to be movable up and downward. Grooves 26 and 27 for holding the winker operation lever stated above at its neutral position are formed in these fixed and movable cam portions 23 and 25, respectively, and further locking grooves 28 and 29 for holding the winker operation lever at the left and right positions, respectively, are formed in the fixed cam portion 23. This movable cam portion 25 is energized downward by a spring and moved in the locking removing direction, i.e. upward, by a solenoid excited by a removing signal produced e.g. by a returning rotation of the steering wheel, etc.
By the prior art technique described above, in order to locate the winker operation lever at its neutral position without shaking, the compression spring thrusting the driving bar with pressure into the groove 26 formed in the cam should have a certain spring pressure. Consequently, when the driving bar is engaged with the left and right locking grooves 28 and 29, the spring pressure becomes still greater. Since the movable cam portion 3 is moved upward against the compression spring by the excitation of the solenoid, in such a state, so as to compress the driving bar, the spring force of the compression spring at removing the locking is great. Therefore a great solenoid is necessary in order to move the movable cam portion 25 upward against this spring force, which impedes to reduce the size and raises the cost.
Therefore, in order to solve the problem described above, the applicant of the present invention has proposed Japanese Utility Model, application No. 63-61587. This canceling device for a winker comprises, as indicated in FIGS. 6A and 6B, a case 30; a winker operation lever 31 held pivotably by the case 30; a driving shaft 33 mounted extensively on this lever 31 through a compression spring 32; a cam 37 having grooves 34, 35 and 36 holding the lever 31 at the neutral, the left and the right position, respectively, by being engaged with this driving shaft 33; a removing member 39, which is brought into contact with a cam portion 38 disposed on the lever 31 and rotates the lever 31 in the locking removing direction; and a solenoid driving this locking removing member 39 and excited by a returning rotation of the steering wheel.
Consequently, since the winker operation lever 31 is rotated in the locking removing direction through the removing member 39 by the excitation of the solenoid, the compression spring 32 is not compressed directly by the solenoid and therefore no solenoid having a great force for compressing the compression spring 32 is needed. Further, since the whole surface of the contacting portion 39a of the removing member 39 is brought into contact with pressure with the cam portion 38 at the neutral position, this neutral position is held further stably so that fluctuations are prevented. Further, since the spring force of the compression spring 32 can be small, the force needed for the operation is alleviated. Still further, as indicated in FIG. 6B, since the contact position between the cam portion 38 and the contacting portion 39a of the locking removing member 39 at the left position is away from the pivoting shaft 40, the force required for rotating the winker operation lever 31 may be small. In addition, a spring force of a plate spring is applied to the locking removing member 39, which reduces further the excitation force of the solenoid.
Furthermore the working piece 41 of the solenoid is made of a metal and on the other hand the lever 31 is made of synthetic resin. Therefore, when these two members are slid directly, abrasion of the sliding surface of the lever 31 is great. For this reason, it is possible to reduce the abrasion of the lever 31 by interposing the locking removing member 39 made of synthetic resin therebetween.
Now, by the prior art technique described above, when the lever 31 is pivoted, the contacting position between the cam portion 38 and the contacting portion 39a of the locking removing member 39 is detached from the pivoting shaft 40, i.e. from the center of the working piece 41. Therefore, although the rotational force of the lever 31 may be small as described previously, a non-uniform force is applied to the plunger of the solenoid due to the deviation of the contact point, which gave rise to decrease in the durability and the attractive force of the plunger.
Further, if the contacting surface between the locking removing member 39 and the case is not set so as to be long in some degree, the removing member 39 is apt to be inclined and no sure sliding displacement is secured. This is a serious obstacle at realizing to reduce the size of products. In addition, a force acts on the locking removing member 39 so as to incline it, due to the fact that the contacting position described above is deviated. Consequently, when the contacting surface is shortened for the purpose of reducing the size of the whole device, the inclination of the locking removing member 39 increases further. Furthermore, since the removing member 39 is guided slidably on the two side walls of the case 30, when different members are extended or contracted due to temperature variations, gaps are produced and the locking removing member 39 becomes apt to be inclined.